# No.48 ロボットの操縦
X, Y, L = [int(input()) for i in range(3)]

X = abs(X)
Y = abs(Y)

if X == 0 and Y > 0:
    result = 0
elif Y > 0:
    result = 1
else:
    result = 2

while X > 0:
    result += 1
    X -= L

while Y > 0:
    result += 1
    Y -= L

print(result)